Single MoS₂ Device Classifies ECG Segments in Proof-of-Concept Reservoir Computing

A single contact-engineered molybdenum disulfide memtransistor achieved 93.9% accuracy in distinguishing normal from ventricular ectopic heartbeat segments in a proof-of-concept reservoir-computing experiment. The study, led by Daisuke Kiriya at The University of Tokyo and published in ACS Nano, used 23,818 electrocardiogram segments from the MIT-BIH Arrhythmia Database. The device combined analog memory with time-dependent processing, but the researchers did not present the system as a clinical diagnostic tool.

The team investigated whether memory behavior in a planar MoS₂ memtransistor could be controlled by modifying its electrical contacts rather than adding a switching material throughout the semiconductor channel. Using a solution-based AuCl₃ treatment, the researchers selectively altered the interface where a metal electrode meets MoS₂. Electrical measurements indicated that charge trapping and detrapping at this interface dynamically changed the effective Schottky barrier controlling carrier injection.

The intrinsic MoS₂ channel remained largely unmodified. Temperature-dependent measurements supported a contact-limited transport mechanism. The extracted effective Schottky barrier height was approximately 40.8 meV in the pristine device and approximately 196 meV after AuCl₃ treatment.

Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy were used to examine material and chemical changes associated with the modified interface. Under drain-voltage pulse stimulation, the device produced gradual long-term potentiation and depression, spike-amplitude-dependent plasticity and timing-dependent conductance changes. Its paired-pulse response included both faster and slower temporal components, consistent with more than one interfacial charge-relaxation process.

To apply the device’s temporal dynamics, the researchers operated one memtransistor as the physical reservoir in an ECG-processing system. The single device was used with 10 time-multiplexed virtual nodes, rather than a physical array of devices, and its reservoir responses were analyzed for heartbeat classification. Of the 23,818 heartbeat segments, 19,053 were used for training and 4,765 for testing.

The resulting analysis produced an area under the receiver operating characteristic curve of 0.965 and an overall accuracy of 93.9% when discriminating normal and ventricular ectopic heartbeat classes. Because the switching mechanism is localized at the metal–MoS₂ interface, the study demonstrates that a controlled contact can provide the analog synaptic behavior needed for temporal signal processing without modifying the whole MoS₂ channel. The solution-based treatment also provides a route compatible with lithographic device fabrication and toward planar, independently addressable artificial synaptic devices.

The researchers described the ECG result as a proof of concept for processing temporal signals with the dynamic response of a single contact-engineered device.

Subject of Research: Contact-engineered MoS₂ memtransistors for analog synaptic memory and ECG reservoir computing

Article Title: Contact engineering provides MoS₂ memtransistor with brain-inspired memory for cardiac signal processing

Article References: Contact engineering provides MoS₂ memtransistor with brain-inspired memory for cardiac signal processing. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: MoS₂ memtransistor, contact engineering, artificial synapse, reservoir computing, ECG processing, analog memory, Schottky barrier, charge trapping, neuromorphic computing, ventricular ectopic beats, Contact, engineering